1. Field of the Invention
The present invention relates to semi-fixed ammunition. In particular, the present invention relates to semi-fixed ammunition and is intended to replace the cumbersome, multi-zone, bagged discrete charge system with charge components of a rigid, modular design.
2. Description of Related Art
Historically, the United States military has maintained 105 mm howitzers, which employ semi-fixed ammunition. Semi-fixed ammunition is a design where the projectile is seated on a cartridge canister or case containing a propulsion system. The term “semi-fixed” means that the projectile can be removed from the case mouth and replaced there, permitting access to the internal propellant charge. When ammunition of this type is employed, it is typically used in a multi-zone configuration. In this mode, the projectile is removed and the propellant charge adjusted by removal of one or more of the propellant increments, then the projectile is reseated on the case mouth. The complete round, prepared in this manner, is then inserted into the cannon for firing. In the present generation of howitzers with semi-fixed ammunition, all systems currently employ a plurality of cloth bags to hold the propellant. Zoning is achieved by removing one or more of these bags.
While this system has proven useful over the years, it is not without its limitations. Firstly, it is not a system, which can be easily automated, and its rate of fire cannot be increased. Further, there are safety issues associated with the misidentification of charge increments, and deterioration of the cloth bags employed, during long-term storage, has traditionally been a problem. It has recently been determined that, because of the shape and location of the ullage, or empty space within the cartridge canister, internal pressure waves can occur, which can cause adverse, sometimes catastrophic, ignition.
U.S. Pat. Nos. 4,702,167 and 4,864,932 to Reinelt and Schwenzer are entitled Propellant-Charge Module and are assigned to Rheinmetall GmbH, of Germany. These references both claim priority of a single German patent filing, and show a propellant-charge pack of the doughnut-shaped annular type, in which the inner annular wall is provided with an easily ignited primary charge, while the remaining volume of the pack contains propellant.
U.S. Pat. No. 5,180,883 to Jaskolka, Rahnenfuhrer and Schulze, is entitled Ammunition and is assigned to Theinmetall GmbH, of Germany. This reference shows a projectile with primary charge and a projectile charge. In addition, both of these charges are provided with an annular transfer charge at their junctions that permits ignition of the projectile charge without a noticeable time delay relative to the primary charge.
U.S. Pat. No. 5,844,163 to Lindskog, is entitled Loading System and is assigned to Bofors AB, of Sweden. This reference shows a method and device for the automatic loading of doughnut-shaped rigid propellant modules. A stack of the chosen loading modules is prepared and swung into position to be ram-loaded.